modern flute C foot

multiphonic C5 & D#6

Impedance

Fingering a key depressed a key not depressed a part of the mechanism that is not normally touched Details in fingering legend. Acoustic schematic a closed tone hole an open tone hole Non-specialist introduction to acoustic impedance Non-specialist introduction to flute acoustics

This is the standard fingering for D6 and may be compared with that for G6, with the C# hole acting as a register hole. It may also be regarded as a C# with enough cross fingering to flatten it by a semitone. Until the 1950s, playing both notes together would have been regarded as a mistake rather than a multiphonic.

A two-note multiphonic requires the superposition of two standing waves (whose frequencies, which are not in harmonic ratios, determine the pitches). Usually, this is achieved by opening one tone hole in a series of closed tone holes. The wave travelling downstream from the reed is partially reflected at the open tone hole, which makes one standing wave. The rest of the energy in the incident wave continues down the bore, until it reaches the first in a series of open tone holes. Here it is reflected to make the second standing wave.

For this situation to apply, the frequencies of the notes have to be such that the effect of the inertia of the air in the open tone hole is large enough to allow some transmission past the hole, but small enough to produce some reflection. For low-pitched notes, the tone hole is usually small.